Go to www.BootsnAll.com
They have a discount airline ticket operation with a very user friendly search engine.
BUT: Do NOT use them if you are making last minute plans and want to use E-tickets. They will not E-ticket international flights (because apparently the airlines will not pay a commission unless they write a paper ticket) but they do NOT tell you that when you book. I used them and got a good rate to get Izzy tickets from Guatemala City to Panama and then back to North Carolina to pick up his car, but they did not tell me that they would not e-ticket until after I ordered and paid for the flights. I had to pay double fedex charges, wait for fedex to deliver the ticket to me, then fedex it to the hotel in Guatemala City where he will be staying the night before he flies. And they will NOT send tickets to any address outside of the US (they don't tell you that either)...so you can't use them if your flight originates outside the US.
But if you have plenty of time to receive your tickets before you fly and don't mind paper tickets, they are definitely worth looking into.